The proceeds of the bonds shall be used solely for the payment of the cost of the project or combined projects and shall be disbursed upon requisition or order of the chairman of the authority or its duly bonded agents under such restrictions, if any, as the resolution authorizing the issuance of the bonds or the trust indenture may provide. If the proceeds of such bonds, by error of calculation or otherwise, shall be less than the cost of the project or combined projects, unless otherwise provided in the resolution authorizing the issuance of the bonds or in the trust indenture, additional bonds may in like manner be issued to provide the amount of such deficit, which bonds, unless otherwise provided in the resolution authorizing the issuance of the bonds or in the trust indenture, shall be deemed to be of the same issue and shall be entitled to payment from the same fund without preference or priority of the bonds first issued for the same purpose. If the proceeds of the bonds of any issue shall exceed the amount required for the purpose for which such bonds are issued, all surplus shall be paid into the sinking fund provided for the payment of principal and interest of such bonds.